1. Field of the Invention
The invention comprises a method and apparatus for generating soft X-ray lasing action by focusing a powerful picoseond laser on a confined plasma column.
2. Description of the Prior Art
Soft X-ray lasers have gained recent attention because of the interesting scientific potential for such devices. It is believed that X-ray lasers would have the capability of forming holographic interference images which could, for example, be used to study the detailed three-dimensional structure of small molecules such as DNA. Other significant applications are anticipated. The potential for X-ray lasers is described in the Oct. 30, 1984 editions of THE NEWARK STAR LEDGER and THE WALL STREET JOURNAL, as well as the Apr. 2, 1985 edition of THE NEW YORK TIMES.
New technology has made it possible to create very powerful excimer lasers having pulse duration times in the neighborhood of 1 picosecond and powers in the neighborhood of 10.sup.15 -10.sup.17 W/cm.sup.2 and above. Since high power excimer lasers have only recently been possible, there isn't much in the way of prior art that appears relevant to the concept. Of some interest in U.S. Pat. No. 4,058,486 entitled PRODUCING X-RAYS which discusses the formation of a plasma by a low power precursor pulse which is followed up by a subseqent higher power main pulse with the object of creating X-rays from the interaction. A variety of low-Z and high-Z materials are described as potential laser targets. The use of multi-Z plasmas is also discussed in U.S. Pat. No. 4,201,955 in a different laser environment. According to an alternative embodiment of the present invention the CO.sub.2 laser could be replaced by a neodymium glass laser. The use of Nd:G glass lasers is discussed in a different environment in U.S. Pat. No. 4,058,486. Also of possible interest is a publication entitled "Soft X-Ray Pumping of Metastable Levels of Li Plus", Appl. Phys. Lett. 42(1) Jan. 1, 1985, 9-11. While the foregoing devices may have some relevance to the present invention, they are not believed to have the capability of producing the significant soft X-ray lasing action of the method and apparatus disclosed herein.